Completely agree with you. In particular regarding the "motivated students and teachers" aspect I think it probably plays a role in favor of esperanto in these

Completely agree with you. In particular regarding the "motivated students and teachers" aspect I think it probably plays a role in favor of esperanto in these studies. I don't think many people have to learn esperanto at school or for work, clearly it heavily biases towards people who are interested in learning languages and esperanto in particular. You have to be very careful while creating your samples to compensate for that I think. >One of the studies Wikipedia cites claims that you can learn the grammar of Esperanto in ~5 hours, which is "impossible" for other languages. That instead screams to me that Esperanto is taught as a detached grammar course in early instruction, whereas other languages will tend to start with a phonological crash-course combined with basic phrase acquisition, instead spreading grammar out over several hundreds of hours of instruction. That might be true but on the other hand imagine teaching English students a "detached" French grammar for instance. I think the students would give up within the hour, it's too dense and quirky to be palatable. If Esperanto's grammar is really simple and regular and can be integrated in 5 hours it's a good point in its favor.